my dog has some kind of dandruff on fur wondering if it's some kind of mites

my dog has dandruff like white spots on her fur. it is very small but alot of it. Her skin appears very healthy and she's not scratching. It mostly clings to the ends of the fur. I brush it and it comes off. We had her groomed yesterday and it was gone but today it's back. It's not in just one spot, it appears from her head to her tail in different areas. The best way to describe it is it's like she brushed up against very fine ashes. The groomer thought it was dandruff but because it's only on the outside of her fur I'm beginning to think it's some kind of mite or dog lice? Any help would be greatly appreciated. She started with this about 6-8 weeks ago.

Have you changed her food recently?

Have you taken her to a vet to get it checked out?

no change in diet. we thought it was dandruff and so did the groomer. If I don't get any help from this sight i will go the vet. i was hoping a vet could tell me if there is anything like that other than dandruff.